Typical pressure measuring devices measure the difference in pressure between a fluid provided to the device and the ambient or between two discrete fluids. Certain prior art pressure measuring devices employ bourdon tubes, hollow curved tubes pressurized interiorly thereof by one of the fluids and exteriorly thereof by the other fluid or ambient. Pressurization of the interior of the tube tends to straighten it, the movement of the tube end being indicative of the difference in pressure between the fluids. Where it is desirable to employ a bourdon tube to measure the difference in pressure between two discrete fluids, the higher pressure fluid must be provided to the interior of the tube and the lower pressure fluid to the outside thereof. When it is not known which fluid will be of the higher pressure, means are required to distinguish the higher pressure fluid from the lower pressure fluid so that the higher pressure fluid may be applied to the interior of the tube and the lower pressure fluid to the outside thereof. Furthermore, means must be provided to indicate which fluid is of the higher pressure so that the sign of the pressure drop being measured may be determined.
The pressure measuring device of the present invention provides a digital reading of differential pressure magnitude and sign, making the device particularly well suited for use with electronic computers.